U.S. patent application number 12/874351 was filed with the patent office on 2011-03-10 for transfer apparatus and transfer method.
This patent application is currently assigned to MURATA MACHINERY, LTD.. Invention is credited to Masaru HATTORI, Tsuyoshi KUMAZAWA, Takeshi MURAKAMI.
Application Number | 20110056901 12/874351 |
Document ID | / |
Family ID | 43646884 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110056901 |
Kind Code |
A1 |
KUMAZAWA; Tsuyoshi ; et
al. |
March 10, 2011 |
TRANSFER APPARATUS AND TRANSFER METHOD
Abstract
In a transfer apparatus, a SCARA arm is provided on an elevation
platform. Further, a sensor arranged to detect inclination at a tip
end of the arm and a sensor arranged to measure a position of an
article on the arm are provided. A base is tilted to eliminate
inclination of the detected inclination, and a stretching amount of
the arm is corrected in correspondence with the measured position
of the article on the arm.
Inventors: |
KUMAZAWA; Tsuyoshi;
(Inuyama-shi, JP) ; HATTORI; Masaru; (Inuyama-shi,
JP) ; MURAKAMI; Takeshi; (Kyoto-shi, JP) |
Assignee: |
MURATA MACHINERY, LTD.
Kyoto-shi
JP
|
Family ID: |
43646884 |
Appl. No.: |
12/874351 |
Filed: |
September 2, 2010 |
Current U.S.
Class: |
212/276 |
Current CPC
Class: |
B66C 13/18 20130101;
B66C 13/46 20130101 |
Class at
Publication: |
212/276 |
International
Class: |
B66C 13/18 20060101
B66C013/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2009 |
JP |
2009-207880 |
Claims
1. A transfer apparatus comprising: a tiltable base; an arm
configured to be elevated, lowered, stretched, and retracted on the
base; a sensor arranged to detect inclination at a tip end of the
arm; a sensor arranged to measure a position of an article on the
arm; and a controller arranged to tilt the base to cancel a
detected inclination and to correct a stretching amount in
correspondence with a measured position of the article on the
arm.
2. The transfer apparatus according to claim 1, further comprising
an inclination sensor arranged to detect inclination of a moving
element of the inclination sensor caused by gravity, at a tip end
of the arm.
3. The transfer apparatus according to claim 1, wherein the
controller is configured to stretch the arm in correspondence with
the position of the article on the arm at a time of unloading the
article, tilt the base in accordance with a stored tilt angle
during stretching of the arm, and lower the arm while tilting the
base in accordance with a signal from the sensor to detect the
inclination after stretching of the arm.
4. The transfer apparatus according to claim 3, wherein the
controller is configured to elevate the arm while tilting the base
in accordance with a signal from the sensor to detect the
inclination at a time of loading of the article, and retract the
arm while tilting the base in accordance with a stored tilt angle
after elevation of the arm.
5. A method of transferring an article by providing a tiltable base
and an arm configured to be elevated, lowered, stretched, and
retracted on the base, the method comprising the steps of: a)
detecting inclination at a tip end of the arm using a sensor, and
tilting the base to cancel the detected inclination; and b)
measuring a position of the article on the arm, and correcting a
stretching amount of the arm in accordance with the measured
position of the article on the arm.
6. The transfer method according to claim 5, wherein the step (a)
is carried out at a time of elevating or lowering the arm, and the
method further comprises the step (c) of tilting the base in
accordance with a stored tilt angle at a time of stretching or
retracting the arm.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a transfer apparatus. In
particular, the present invention relates to a transfer apparatus
capable of unloading an article to a predetermined position without
any inclination of an arm at a time of stretching the arm.
[0003] 2. Description of the Related Art
[0004] The applicant proposed to attach an optical sensor to a tip
end of an arm of a slide fork or the like, for reading a mark near
a support member to correct inclination of the arm. See, for
example, JP 2006-219233A. However, in the case of reading the mark
near the support member, areas where inclination can be detected
are limited to narrow ranges immediately before a loading position
and immediately before an unloading position. In other positions,
inclination can only be corrected by means of an open loop control
in accordance with a stored pattern. Under such circumstances,
since inclination of the arm cannot be corrected sufficiently at
the time of unloading the article, the article may contact a guide
near the support member, and the article may be unloaded to a
position shifted from an intended position. Further, since no
sensor is provided for measuring a position of the article in a
length direction of the arm, at the time of unloading the article,
the guide may easily contact the article to cause a further shift
of the unloading position of the article.
SUMMARY OF THE INVENTION
[0005] Preferred embodiments of the present invention make it
possible to transfer an article while keeping a tip end of an arm
horizontal, and to unload the article to a more correct
position.
[0006] In addition, preferred embodiments of the present invention
make it possible to measure inclination regardless of a position in
an elevation direction of the arm, without requiring any marks or
the like at the destination of transfer of the article.
[0007] Also, preferred embodiments of the present invention provide
a specific method of unloading an article to a correct position
quietly.
[0008] According to a preferred embodiment of the present
invention, a transfer apparatus includes a tiltable base, an arm
arranged to be elevated, lowered, stretched, and retracted on the
base, a sensor arranged to detect inclination at a tip end of the
arm, a sensor arranged to measure a position of an article on the
arm, and a controller arranged to tilt the base to cancel a
detected inclination and to correct a stretching amount of the arm
in correspondence with a measured position of the article on the
arm.
[0009] In this manner, by tilting the base, inclination at the tip
end of the arm can be eliminated. At the time of unloading the
article, collision between the arm and the guide at the unloading
position due to inclination of the arm can be prevented. Further,
by eliminating inclination at the tip end of the arm, the elevation
distance of the arm required to load and unload the article can be
shortened. Further, by measuring the position of the article on the
arm, the unloading position is corrected in correspondence with the
position of the article. Therefore, also in this respect, collision
with the guide or the like is prevented, and the article can be
unloaded to the correct position. Thus, the article can be
transferred to the correct position quietly.
[0010] Preferably, as a sensor to detect the inclination, an
inclination sensor to detect inclination of a moving element due to
the gravity is provided at the tip end of the arm. In this manner,
inclination at the tip end of the arm can be detected in a wide
range regardless of the position in the elevation direction of the
arm. Further, no marks or the like are required at the destination
of the transfer of the article.
[0011] Further, preferably, the controller is configured to stretch
the arm in correspondence with the position of the article on the
arm at the time of unloading of the article, tilt the base in
accordance with a stored tilt angle during stretching of the arm,
and lower the arm while tilting the base in accordance with a
signal from the sensor arranged to detect the inclination after
stretching of the arm. During stretching of the arm, since
acceleration in the horizontal direction is applied to the
inclination sensor, it is difficult to correctly measure the
inclination. Therefore, during this period, the base is tilted in
accordance with the stored tilt angle. At the time of lowering the
arm after the arm has been stretched, since only the gravity is
applied to the inclination sensor, and the inclination sensor is
accelerated only in the direction of gravity (vertical direction),
inclination can be measured correctly. Therefore, at the time of
lowering the arm, the base is tilted in accordance with the signal
from the inclination sensor. In this manner, in the period from
stretching of the arm, elevation of the arm, and until unloading of
the article, the tip end of the arm can be kept substantially
horizontal all the time so as to make it possible to unload the
article to a predetermined position.
[0012] More preferably, the controller is configured to elevate the
arm while tilting the base in accordance with a signal from the
sensor arranged to detect the inclination at the time of loading of
the article, and retract the arm while tilting the base in
accordance with a stored tilt angle after elevation of the arm. In
this manner, during the period from loading of the article until
transportation of the article onto the base, the tip end of the arm
can be kept substantially horizontal all the time.
[0013] In a preferred embodiment of the present invention, a
tiltable base and an arm configured to be elevated, lowered,
stretched, and retracted on the base are provided, and an article
is transferred by performing by the steps of a) detecting
inclination at a tip end of the arm using a sensor, and tilting the
base to cancel the detected inclination, and b) measuring a
position of the article on the arm, and correcting a stretching
amount of the arm in accordance with the measured position of the
article on the arm.
[0014] Preferably, the step (a) is performed at the time of
elevating or lowering the arm, and the step (c) of tilting the base
in accordance with a stored tilt angle is performed at the time of
stretching or retracting the arm.
[0015] In the present specification, the description regarding the
transfer apparatus is directly applicable to the transfer method,
and conversely, the description regarding the transfer method is
directly applicable to the description regarding the transfer
apparatus.
[0016] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a plan view showing main components of a transfer
apparatus according to a preferred embodiment of the present
invention.
[0018] FIG. 2 is a side view showing main components of the
transfer apparatus according a preferred embodiment of the present
invention.
[0019] FIG. 3 is a block diagram showing an inclination sensor used
in a preferred embodiment of the present invention.
[0020] FIG. 4 is a block diagram showing a controller included in a
preferred embodiment of the present invention.
[0021] FIG. 5 is a flow chart showing a loading algorithm used in a
preferred embodiment of the present invention.
[0022] FIG. 6 is a flow chart showing an unloading algorithm used
in a preferred embodiment of the present invention.
[0023] FIG. 7 is a side view schematically showing a support member
and an article at the time of unloading.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Hereinafter, preferred embodiments for carrying out the
present invention in the most preferred form will be described. The
scope of the present invention shall be determined according to the
understanding of a person skilled in the art based on the
description of the claims in consideration of the description of
the specification and techniques known in this technical field.
[0025] FIGS. 1 to 7 show a stacker crane 2 taken as an example of a
transfer apparatus according to a preferred embodiment of the
present invention. A transfer apparatus according to a preferred
embodiment of the present invention may be mounted in an automatic
transportation vehicle, an overhead traveling vehicle or the like,
for example. Alternatively, instead of mounting the transfer
apparatus in the vehicle, a body of the transfer apparatus may be
attached to a tiltable base provided on a station or the like, for
example. In the drawings, a reference numeral 2 denotes a stacker
crane that travels on travel rails 3. A reference numeral 4 denotes
vehicle, and a reference numeral 6 denotes an elevation platform
that is elevated and lowered along a mast 7. Reference numerals 8
denote a frame, e.g., provided on front and back sides of the
elevation platform 6. Reference numerals 10 denote guided members,
and each of the guided members 10 is connected to the frame 8
through a pivot central shaft 34 and a tilt shaft 36 described
later. The guided members 10 are guided by the mast 7, and elevated
and lowered by elevation members 12 such as chains, belts, or
ropes. Reference numerals 14 denote tilt motors arranged to control
an inclination angle (tilt angle) of the elevation platform 6
relative to a horizontal plane.
[0026] For example, a turntable 16 is provided on the elevation
platform 6, and a pair of SCARA arms 18 are mounted on the
turntable 16. Reference numerals 19, 20 denote arms of the SCARA
arms 18, and reference numerals 21 to 23 denote shafts. A reference
numeral 26 denotes a hand attached to distal ends of the pair of
the SCARA arms 18. Instead of the SCARA arms 18, for example, a
slide fork may be used. The turntable 16 may not be provided. The
hand 26 supports the article in an area on the right side of a
dotted line in FIG. 1. The area for supporting the article is
referred to as the tip end. A reference numeral 28 denotes an
inclination sensor provided at the tip end of the hand 26 to
measure inclination from the horizontal plane. A reference numeral
30 denotes an article position sensor arranged to measure a
position of the article on the hand 26. For example, a laser
distance sensor may be used as the article position sensor 30. A
reference numeral 32 denotes a controller of the stacker crane
2.
[0027] FIG. 2 shows a tilt mechanism of the elevation platform 6.
The frame 8 is connected to the guided member 10 at one of upper
and lower positions of the tilt mechanism. The frame 8 is pivotable
about the pivotal shaft 34. A tilt shaft 36 is fixed to the other
of the upper and lower positions of the guided member 10. As shown
in an upper left portion in FIG. 2, the tilt shaft 36 is movable to
the left and right within a long hole 42 provided in the frame 8.
The tilt shaft 36 is connected to a ball screw 38 attached to a
tilt motor 14 through a nut 40. In this manner, the tilt shaft 36
can move relative to the long hole 42 by the tilt motor 14. Since
the elevation platform 6 is pivotable about the pivot central shaft
34, the elevation platform 6 can be inclined (tilted) toward the
left or right in FIG. 2. The tilt mechanism is not limited to the
mechanism shown in FIG. 2. For example, by supporting four corners
of the elevation platform 6 by the elevation members, and by
feeding the elevation members on the left and right sides of the
elevation platforms 6 by different amounts, the elevation platform
6 is tilted. In the present preferred embodiment, the transfer
apparatus includes the elevation platform 6, components on the
elevation platform 6 such as the SCARA arms 18, the tilt mechanism,
and the elevation mechanism of the elevation platform 6.
[0028] FIG. 3 shows structure of the inclination sensor 28. A
reference numeral 43 denotes a power supply, and reference numerals
44 to 46 denote resistors. Among the resistors 44 to 46, the
voltage of the resistor 46 is outputted. A reference numeral 48
denotes a coil, a reference numeral 49 denotes a yoke made of
magnetic material, a reference numeral 50 denotes a rotor made of
magnetic material. When the coil 48 is energized, the rotor 50 is
induced to be in alignment with the yoke 49. A shield plate 51 is
attached to the rotor 50 in the direction of gravity. When the
inclination sensor 28 is inclined, due to gravity, the shield plate
51 and the rotor 50 move together to the left or right. Reference
numerals 52, 53 denote LEDs, and reference numerals 54, 55 denote
phototransistors. Photodiodes or the like may be used instead of
the phototransistors. When the inclination sensor 28 is inclined,
the shield plate 51 is tilted, and light from one of the LEDs 52,
53 is interrupted. When the light is interrupted, resistance of one
of the phototransistors 54, 55 is increased, and electrical current
flows through the coil 48 and the resistor 46. By the electrical
current flowing through the coil 48, inclination of the rotor 50
and the shield plate 51 is eliminated, and a feedback for the
inclination by the gravity of the shield plate 51 is provided. As a
result, the electrical current flowing through the resistor 46
becomes substantially proportional to the inclination angle of the
inclination sensor 28. The inclination sensor 28 is not limited to
a sensor arranged to detect inclination of the pendulum (shield
plate 51) due to gravity. Alternatively, a sensor having a moving
element moving along a circular arc route in a vertical plane, and
detecting the position of the moving element may be adopted. It is
desirable to damp vibration of the moving element by providing a
feedback to cancel inclination of the moving element, specifically
by energizing the coil 48 and attracting the moving element by the
yoke 49.
[0029] FIG. 4 shows a controller 32 of the stacker crane 4. A
travel controller 56 controls travel of the vehicle, and uses data
of a position of the vehicle in a traveling direction, measured by
a linear scale 57. An elevation controller 58 uses height data of
the elevation platform 6, e.g., measured by a linear scale 59 to
elevate or lower the elevation platform 6, and thus, elevate or
lower the arms. Further, the elevation controller 58 elevates or
lowers the elevation platform 6 to cancel (offset) the change at
the position of the tip end of the arm due to vibration. Any type
of sensor can be used for measuring the position of the vehicle in
the travel direction and the position in the height direction. At
the time of stretching or retracting the SCARA arms 18, the
elevation controller 58 implements damping control by elevating or
lowering the elevation platform 6, e.g., in accordance with data in
a damping control pattern memory 60 to damp vibration at the tip
end of the hand. The damping control reduces vibration caused by,
e.g., tilt control by a tilt motor, stretching and retraction of
SCARA arms, and the change in the load by the transfer of the
article. The tilt controller 62 implements tilt control to keep the
tip end of the hand horizontal using a signal from the inclination
sensor 28. At the time of stretching or retracting the arms, since
acceleration is applied to the inclination sensor 28 in the
horizontal direction, it is difficult to obtain data of the correct
inclination angle. Therefore, the tilt is corrected in accordance
with a pattern stored in a memory 63 for each of the cases where
any article is present and no article is present. A turntable
controller 64 controls a turntable based on a signal from an angle
sensor such as an encoder 65. An arm controller 66 stretches and
retracts the SCARA arms based on a signal from the article position
sensor 30 to determine the stretching amount of the arms at the
time of unloading the article.
[0030] FIG. 5 shows control at the time of loading an article.
During stretching of the arms, since acceleration in the horizontal
direction is applied, it is difficult to obtain correct data from
the inclination sensor. Therefore, tilt control of the elevation
platform is implemented in accordance with a pattern stored in a
memory, and inclination at the tip end of the arms is eliminated.
Further, since the tip end of the arms is vibrated in a vertical
direction as a result of tilt control and stretching of the arms,
damping control in the elevation direction is implemented by
elevating or lowering the elevation platform for damping vibration
at the tip end of the arms.
[0031] After the end of stretching of the arms, the arms are
elevated by elevating the elevation platform. As shown on the right
side of FIG. 5, elevation of the arms occur in a segment L1 having
a large elevating speed, a segment L2 having a small elevating
speed for loading an article from a support member, and a segment
L3 having a large elevating speed after the segment L2. In the
segments L1 to L3, since no acceleration is applied in the
horizontal direction, by determining an inclination angle using the
inclination sensor to implement feedback control of the tilt shaft,
inclination is corrected to keep the tip end of the arms (tip end
of the hand) horizontal. By operation of the tilt shaft and the
change in the load due to transfer of the article, vibration occurs
at the tip end of the arms. Therefore, the elevation platform is
elevated or lowered to cancel the vibration.
[0032] Also at the time of retracting the arms, since acceleration
in the horizontal direction is applied, it is difficult to
accurately determine the inclination angle by the inclination
sensor. Therefore, the tilt shaft is controlled in accordance with
a pattern stored in the memory. The stored pattern for the tilt
control in the case where any article is present is different from
the stored pattern in the case where no article is present.
Further, the stored pattern at the time of stretching the arms is
different from the stored pattern at the time of retracting the
arms. As the stored pattern, a tilt angle is stored for every
stretching amount of the arms. The elevation platform is elevated
or lowered to cancel vibration at the tip end of the arms due to
the control of the tilt shaft and retraction of the arms.
[0033] In the present preferred embodiment, the inclination angle
at the tip end of the arms can be measured over the entire range at
the time of elevating and lowering the arms. However, in the case
of reading marks of the support member using an optical sensor, the
tilt angle can be detected only in narrow segments. Therefore, in
the other segments, since feedback control cannot be implemented in
a manner to eliminate the inclination angle, the arms and the
article may contact at a line not on a plane, or the article after
loading may contact the support member.
[0034] FIG. 6 shows control of unloading an article. At the time of
loading the article by the arms, or at the time of unloading the
article from the arms, based on the distance to the article
measured by the article position sensor, the stretching amount of
the arms is corrected. Thus, in FIG. 7, the article 72 can be
unloaded to a predetermined position of a support member 70 in a
length direction. The tip end is inclined due to stretching of the
arms. However, since acceleration is applied in the horizontal
direction, it is difficult to determine the inclination angle using
the inclination sensor. Therefore, the inclination angle is
corrected in accordance with a stored pattern in the memory. In the
elevation controller, damping control is implemented by elevating
or lowering the elevation platform to cancel vibration at the tip
end of the arms. The damping control may be omitted.
[0035] At the time of unloading the article by lowering the
elevation platform to lower the arms, as in the case of FIG. 5,
different lowering speeds are used in the three segments L1, L2,
and L3. In each segment, feedback control of the tilt shaft is
implemented based on the inclination angle determined by the
inclination sensor. Through the feedback control, the tip end of
the arms is kept horizontal. Damping control is implemented by the
elevation controller to cancel the vibration by operation of the
tilt shaft and the vibration at the tip end of the arms due to
transfer of the article. At the time of retracting the arms,
inclination is corrected in accordance with the stored pattern for
the case of retracting the arms without any article. Thus, the tilt
shaft is controlled, and vibration control is implemented to cancel
vibration at the tip end of the arms.
[0036] In FIG. 7, the reference numeral 70 denotes the support
member, and a reference numeral 71 denotes a guide such as a ball
like roller. At the time of unloading the article 72, when the arms
are not present at predetermined positions, the arms are guided by
the guide 71. For example, the article 72 is a case of a flat panel
such as a liquid crystal panel or a plasma panel. However, any
article can be the target of transfer in the embodiment. Since the
article position sensor 30 measures the distance to article 72 on
the hand 26, the article can be unloaded to a predetermined
position of the support member 70 in the depth direction. In
particular, when the article 72 is moved repeatedly in a warehouse,
positional deviation of the article 72 relative to the hand 26 is
accumulated to cause a large cumulative deviation (error). However,
in the present preferred embodiment, since the positional deviation
is eliminated each time unloading of the article is carried out,
the positional deviation is not accumulated. Further, since the
inclination sensor 28 measures inclination at the tip end of the
hand 26, and eliminates inclination by operating the tilt shaft,
the article 72 does not collide with components such as the guide
71. Therefore, the article 72 can be unloaded to a correct position
without applying impact or the like to the article 72. Further, the
unloading position of the article 72 can be kept correctly.
[0037] In the present preferred embodiment, though the laser
distance sensor is used as the article position sensor 30, any
sensor can be used as long as it can measure the distance to the
article 72. The position of the article position sensor 30 is not
limited to the rear end of the hand 26. Though the inclination
sensor 28 is provided at the tip end of the hand 26 (portion for
supporting the load of the article 72), the inclination angle based
on the elevation platform may be measured, e.g., using a camera
provided in the elevation platform. In the present preferred
embodiment, damping control is implemented at the time of
retracting the arms without having any article after unloading and
at the time of stretching the arms without having any article
before loading. However, the damping control for the arms without
having any article may be omitted. Further, the damping control may
entirely be omitted.
DESCRIPTION OF THE NUMERALS
[0038] 2: stacker crane [0039] 3: travel rail [0040] 4: vehicle
[0041] 6: elevation platform [0042] 7: mast [0043] 8: frame [0044]
10: guided member [0045] 12: elevation member [0046] 14: tilt motor
[0047] 16: turntable [0048] 18: SCARA arm [0049] 19, 20: arm [0050]
21 to 23: shaft [0051] 26: hand [0052] 28: inclination sensor
[0053] 30: position sensor for articles [0054] 32: controller
[0055] 34: pivotal shaft [0056] 36: tilt shaft [0057] 38: ball
screw [0058] 40: nut [0059] 42: long hole [0060] 43: power supply
[0061] 44 to 46: resistor [0062] 48: coil [0063] 49: yoke [0064]
50: rotor [0065] 51: shield plate [0066] 52, 53: LED [0067] 54, 55:
phototransistor [0068] 56: travel controller [0069] 57, 59: linear
scale [0070] 58: elevation controller [0071] 60: damping control
pattern memory [0072] 62: tilt controller [0073] 63: memory [0074]
64: turntable controller [0075] 65: encoder [0076] 66: arm
controller [0077] 70: support member [0078] 71: guide [0079] 72:
article
[0080] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *